Monthly Archives: November 2015

Butterflies and pesticides – a new study and a smoking gun

Gatekeeper cropped P1010472

Following hot on the trail of the raft of recent papers that I highlighted on the blog last week comes a new study by Andre Gilburn and colleagues entitled “Are neonicotinoid pesticides driving declines of widespread butterflies?“.  The paper is open access and published in the journal PeerJ which encourages post-publication comments and review of the work.  I see that Tom Oliver of the Centre for Ecology and Hydrology has started the ball rolling with a couple of questions, and hopefully more will follow, with responses from the authors.

The paper focuses on the fact that between 2000 and 2009 there was a 58% decline in butterfly abundance on farmed land in the UK despite a doubling of spending on conservation in the UK over the same period, much of it on agri-environmental schemes on that very same farmed land.

Using a statistical modelling approach the authors conclude that the introduction of neonicotinoid pesticides in the mid-1990s is strongly implicated as a likely driver of those declines.  My immediate question on reading the paper was: “What were the trends like before the mid-1990s, and did the rate of decline change significantly after that period?”

The authors don’t directly answer the question but it seems to me to be quite an important one to answer because abrupt changes in rates of decline in the abundance and diversity of species can be linked to broader changes in, for example, land management and agricultural practices, as we showed recently for bee and wasp extinctions in Britain.

So I looked for the data that would tell me whether the trend had changed and found what I needed in the UK Butterfly Monitoring Scheme annual report for 2014.  Here’s a screen grab of Figure 3 from the report:

Butterfly abundance indices - November 2015

I’ve marked the point at which neonicotinoid pesticides were starting to be widely used in UK farming with a black line.  As you can clearly see this is also roughly the point at which the abundance of the 24 “Species of the wider countryside” begins to trend downwards.  In comparison, the 26 “Habitat specialists” show much less of a change, and in fact their initial decline was much earlier (in the 1970s-80s), possibly in response to loss of species rich grassland and ancient woodland.

Of course I’m just eyeballing the data and it needs to be tested statistically to see if there really is a break point in the trend at the mid-1990s, but this ought to be possible for anyone with access to the full data set.  Even if this is shown to be the case it’s all correlative (as Gilburn and colleagues acknowledge) and proving causation is difficult.  Nonetheless it looks to me like there’s an interesting smoking gun here that deserves further study.

Pollinators seminar at the Houses of Parliament – 2nd December

Skipper on ragwort - cropped

The Parliamentary Office of Science and Technology (POST) has organised a “Pollinators Update” afternoon seminar in London on Wednesday 2nd December, to discuss recent developments in pollinator conservation research. I’ve been asked to give a 15 minute presentation on the pollinator extinctions research we published in Science last year.

The full programme will be:


  • 2.30pm Sarah Newton MP, Chair’s Welcome
  • 2.40pm Presentations
  • Professor Simon Potts (Professor of Biodiversity and Ecosystem Services) – Reading University
  • Professor Jeff Ollerton (Professor of Biodiversity) University of Northampton
  • Dr Claire Carvell – NERC Centre for Ecology and Hydrology
  • Dr Richard Gill – Imperial College London
  • 3.40pm Discussion
  • 3.55pm Chair’s closing remarks
  • 4.00pm Refreshments


The seminar is free to attend but you need to book a place: see the POST website for details.

Pesticides and pollinators: some new studies and contrasting conclusions

Bee on apple blossom - 1st May 2015

The question of whether or not neonicotinoid pesticides are negatively impacting agricultural pollinator abundance, diversity and behaviour continues to focus the minds of researchers. It’s an issue that has been almost constantly in the news since the earliest suggestions that these pesticides were harming pollinators. These concerns have led to temporary EU restrictions on the use of these chemicals, a decision that was partially over turned this year in the UK.

The past two months has seen the publication of at least five papers on the topic, two of them this week alone.  In this post I want to highlight those papers and provide some commentary.

The first two studies have shown that neonicotinoid pesticides can affect pollinator behaviour, and specifically the memories of both honey bees and bumblebees:

Wright et al. “Low doses of neonicotinoid pesticides in food rewards impair short-term olfactory memory in foraging-age honeybees

Stanley et al. “Bumblebee learning and memory is impaired by chronic exposure to a neonicotinoid pesticide“.

Subtle behavioural changes such as those documented here are not generally assessed in standard toxicological safety assessments for pesticides, which are mainly focused on whether or not the chemicals kill non-target animals, and at what dosage.  But for plant-pollinator interactions (including agricultural pollination) such changes in pollinator behaviour could be crucial to the effectiveness of the pollinators.  How crucial?  Well up until today we didn’t know; but with the publication of another paper by Stanley and colleagues we now have evidence that the sub-lethal effects on pollinator behaviour can actually translate into an effect on pollination of apple crops:

Stanley et al. “Neonicotinoid pesticide exposure impairs crop pollination services provided by bumblebees“.

The study is the first one to my knowledge that tests the effects of field-relevant doses of pesticides on pollinator performance and subsequent pollination services in a commercial farm crop, and adds some valuable hard data to an already heated debate.  The story, embargoed until this evening, has already been picked up by media, including the BBC News website.

To summarise the study: using artificial bumblebee colonies and caged apple trees Stanley and colleagues implemented an experiment in which they tested the effect of two different levels of exposure to a neonicotinoid pesticide on pollinator behaviour and subsequent pollination services to the fruit trees. They found a clear effect of exposure to the higher level of pesticide, resulting in a change in bee behaviour and a subsequent reduction in apple quality.

By way of a contrast, another study this week has focused on the lethal effects of these pesticides.  Henry et al. “Reconciling laboratory and field assessments of neonicotinoid toxicity to honeybees” has shown that although the chemicals are lethal to individual honey bees, the overall impact of the loss of the bees is buffered by the fact that the colonies can simply produce more worker bees to compensate for the losses.  This is interesting but needs to be judged in the context of the fact that honey bees are very unusual and atypical compared to most other pollinators, and indeed most other bees.  They produce very, very large colonies with a unique social structure, and so this compensation might be expected.  These caveats were echoed by some of the scientists asked to comment on the study in media stories such as the one on the BBC News website.

Finally, Godfray et al. have updated their earlier review of the environmental effects of these pesticides with “A restatement of recent advances in the natural science evidence base concerning neonicotinoid insecticides and insect pollinators“.  Given the rate at which new studies are coming out, it won’t be long before a second restatement is required!

Where does this leave the whole debate around pesticides?  Still with firmly entrenched views on both sides I would have imagined.  No doubt the debate will run and run.

Meanwhile, important as it is, the focus on pesticides is in danger of over-shadowing other really interesting studies that might affect how we manage our agro-ecosystems in the UK.  For example, I’d completely missed a paper from the end of September by Pywell et al. entitled “Wildlife-friendly farming increases crop yield: evidence for ecological intensification“.  As far as I can judge from the Altmetric information for the paper, so too had the media: it received no coverage on any of the usual outlets.  But this is important stuff that deserves wider publicity: it’s going to take more than a ban on pesticides to recover some of the biodiversity (at both a species and a habitat level) that we’ve lost due to intensive farming over the last 100 years or so.


What’s wrong with the New Scientist story about “Bumblebees deployed to spray crops with pesticides”?

Here’s a link to the story:

Bumblebees deployed to spray crops with pesticides

There’s at least three things wrong with this story:

  1. The accompanying image is of a honey bee, not a bumblebee.
  2. Bumblebees have nests, not hives.
  3. It’s a dumb idea. For a whole set of reasons, some of which are mentioned by scientists who were interviewed for the story.  I’d add another one: these bees will visit a lot of other flowers besides the ones that are being targeted, potentially spreading the bio-control fungus far and wide in the environment.  Is that really a good idea?

Two of these things are within the control of New Scientist.

Thanks to my colleague Dr Wanda McCormick for pointing out the story.

Pollination syndromes: a brief update on recent developments, and news that Stefan Vogel has passed away

Bee on Salvia - OBG - November 2015

In a recent post I discussed the current debates about “pollination syndromes”, which I described as “sets of flower characteristics that have repeatedly evolved in different plant families due to the convergent selection pressures applied by some groups of pollinators”.

The authors of the Ecology Letters paper that I discussed (Rosas-Guerrero et al. 2014) have now replied to our original critique of their approach and you can read that reply (Aguilar et al. 2015) in Journal of Pollination Ecology by following this link.  Readers can make up their own minds as to whether the authors have responded adequately to our concerns, but I just briefly wanted to raise three points.

The first is that much of these authors’ response is focused on an earlier paper of ours (Ollerton et al. 2009) rather than on our critique per se.  Nick Waser, Mary Price and myself have therefore written a second response that deals with some of the misunderstandings apparent in that piece; it’s available to download here.

The second point relates to the existing literature on pollination syndromes and pollinator effectiveness used by Rosas-Guerrero et al. (2014); as we demonstrated in our critique this is clearly a biased data set that is skewed towards groups of plants with relatively large flowers, “interesting” pollination systems, and text book examples of classical pollination syndromes such as bird and bat pollination.  Researchers who study flowers and their pollinators choose their subjects based on a whole set of criteria, but random selection is not one of them.  However as far as we can judge, Aguilar et al. (2015) seem to be arguing that drawing strong, “universal” conclusions about syndromes from this highly biased data set is perfectly acceptable because of the statistical rigour of formal meta-analysis. I’d re-iterate our main point that no amount of statistical rigour and exhaustive literature searching can take into account inherent biases within the primary data (i.e. the literature itself).

Finally, Aguilar et al. (2015) claim that “human disturbance of natural habitats has caused disruptions in patterns of mutualistic interactions that may partly explain the presence of the diverse pollinator assemblages that are frequently found in pollination studies”.   It seems to us to be disingenuous to argue that pollination syndromes are universally valid and then to essentially concede that there are lots of wrong visitors (“secondary” pollinators), and to explain that with the idea that everything is disturbed in the Anthropocene.  If this is really the case then we probably need to throw out a lot of our understanding of evolutionary ecology as a whole, not just studies of plant-pollinator interactions.

Clearly we don’t accept this argument and in fact it has echoes of arguments that have been going on since the 19th century (Waser et al. 2011): more than 130 years ago the Darwinian biologist Hermann Muller was criticising Federico Delpino (one of the original architects of the idea of pollination syndromes) for ignoring the “wrong” flower visitors.  Interestingly, Delpino was a fundamentally a teleologist who saw purpose in nature, expressed through (as he perceived them) the highly ordered relationships between flowers and pollinators.

As we discuss in the Waser et al. (2011) paper, Stefan Vogel was another prominent pollination biologist, and advocate of the importance of pollination syndromes, who was also fundamentally teleological in his thinking.  I was sad to learn that Stefan passed away very recently, in what I believe is his 90th year.  I was fortunate enough to meet Stefan at a symposium in honour of his 80th birthday at the International Botanical Congress in Vienna in 2005.  He graciously signed my copy of The Role of Scent Glands in Pollination and said, with a twinkle in his eye, “you and I have probably got a lot to discuss”. Unfortunately we never got the opportunity, but later I dedicated our 2009 paper on Ceropegia pollination to him “in honour of his pioneering work on pollination” in the genus.  Stefan’s legacy of research, particularly in the tropical regions of South America, is a fitting tribute to his memory.

Pollination syndromes clearly continue to attract much interest in the scientific literature, and just this week I was intrigued to see a paper by John Benning showing that a species of Ericaceae that looks as though it “should” be pollinated by bees is actually moth pollinated.  No doubt the discussion of the evolutionary extent and predictability of pollination syndromes will continue for some time to come.

A new bee for Northamptonshire!

Anthophora bimaculata 2 cropped P1120172 copy

Back in the summer I produced a series of posts for Pollinator Awareness Week highlighting the pollinators to be found in our own urban garden in Northampton.  One of those posts was of what I believed to be the Little flower bee (Anthophora bimaculata), a species which at the time I’d never previously seen.  I noted that this was a new urban record for Northampton as my PhD student Muzafar Sirohi had not recorded it during his bee surveys, which I discussed earlier this year.

Some time later I checked the bee records on the National Biodiversity Network (NBN) Gateway site and realised that not only was this the first urban record of the species in Northampton, it was actually the first record for the county of Northamptonshire as a whole!  The record has recently been accepted on iRecord and will be added to the NBN records.

Of course this is personally exciting (a new record for a large county found in our back garden) and it adds a significant regional record to the currently known distribution of the species.  The map on the BWARS account of Anthophora bimaculata shows that the species is predominantly southern in its distribution, with a few eastern and western outliers.  This new record places the species firmly in the centre of England, confirming that it is more widespread than previously assumed.

There are two possible explanations for the discovery of this bee in Northamptonshire.  One is that it’s a very recent range expansion and the species is becoming more common and widespread, perhaps as a result of climate change.  The second is that it’s always been present in Northamptonshire, but just never recorded.  At the moment it’s impossible to decide between these two possibilities as there’s evidence to support both.  Not only did Muzafar not record A. bimaculata in his surveys in 2012, neither did Dr Hilary ErenlerDr Sam Tarrant or Kathryn Harrold in their pollinator surveys in the region between 2007 and 2015. Having said that, we do know that Northamptonshire is a historically under-recorded county for bees as it has no County Recorder for Hymenoptera, and both Hilary and Muzafar recorded species new to Northamptonshire, which I hope to report on at a later stage.

Differentiating between these two scenarios will be difficult and may be impossible unless we can discover previously unknown historical specimens of this bee that were collected in the county, or the species continues to expand in its range.

Understanding the distribution of pollinators such as bees is a key component of initiatives such as the National Pollinator Strategy – if we don’t know where the things we are trying to conserve actually are, how can we conserve them?  So it’s very pleasing to be able to make a small contribution to that process from the comfort of our own garden!

Anthophora bimaculata 1 P1120172

Virtual Conference on Pollinators, Pollination and Flowers

B pasc on sunflower

Academic conferences are an important part of what makes science function, via the exchange of ideas and information, publicly and in person.  The act of sitting and listening to both established and early career researchers discussing their most recent work, sometimes before it’s in print, is stimulating and exciting, and will never be replaced by digital technology. We’re social animals and conferences, as much as anything else, are social events.

But conferences are becoming more expensive, more frequent, and increasingly out of reach to researchers with limited budgets.  They are also getting larger: how many times have you attended a big conference and been torn between which of two (or three or four) talks to go to in parallel sessions?  Wouldn’t it be nice to be able to see all of them?  Or to go back and hear again the talks that you most enjoyed?  Likewise, wouldn’t it be great if your students or members of the public could also see what such conference presentations are like?

With this in mind, some time ago I dreamed up the idea of “virtual conferences” in as an experiment that aims to bring together into one place the most interesting recorded seminars, webinars, conference talks and public lectures that are freely available, and present them as a series of themed mini-conferences.  All of the videos in these collections are available on sites such as YouTube* and my role is just to curate them and present them in one place for convenience, as a showcase for some of the best research in biodiversity, evolutionary biology, ecology and conservation, very broadly defined, including inter-disciplinary and policy-related presentations.  And just as at a conference, there’s an opportunity to discuss the talks in the comments section on each post and to provide links to other talks on the same topic.

As well as being a service to the research community and the wider public, I hope that these conferences will be a useful teaching resource at advanced undergraduate and postgraduate level.

If anyone is interested in guest-curating a set of presentations in their own subject area on this blog, please do get in touch and I’ll be happy to talk about it.

So here’s the first virtual conference, on (naturally) pollinators, pollination and flowers:


Judith Bronstein (University of Arizona)

The conservation biology of mutualism


Peter Crane (University of Chicago)

The origins of flowers


Jeffery Pettis (USDA Bee Research Laboratory, Maryland)

The role of pesticides in declining pollinator health


Linda Newstrom (Landcare Research, New Zealand)

Pollinator systems in New Zealand and sustainable farming fund


Mace Vaughan and Eric Mader (Xerces Society/USDA/University of Minnesota)

Pollinator habitat assessment and establishment on organic farms


Carlos Vergara, Rémy Vandame, and Peter Kevan (Universidad de las Americas-Puebla/El Colegio de la Frontera Sur/CANPOLIN)

Coffee pollination in the Americas


Claire Kremen (University of California, Berkeley)

Restoring pollinator communities in California’s agricultural landscapes


*I’m assuming that, as all of these videos are in the public domain, none of the presenters or copyright owners objects to them being presented here.  If you do, please get in touch and I’ll remove it.